1. Field of the Invention
The present invention relates to an image forming unit mountable in an image forming apparatus and a toner cartridge detachable from the image forming unit.
2. Description of the Related Art
A developer cartridge (hereinafter “toner cartridge”) is detachably mounted in an image forming unit (hereinafter “process cartridge”) that is mounted in an image forming apparatus. The toner cartridge has an opening for supplying a toner to the process cartridge and a valve member for opening/closing the opening. It is detached from the process cartridge after the opening is closed by the valve member to prevent the toner from falling from the opening. However, the toner adhering to the outside of the opening can fall to make the interior of the apparatus or the hand or clothing of the operator dirty. Consequently, the replacement of a toner cartridge has been troublesome for the operator.